- 标题
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- 实验方案
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A Comparative Study of Gas Sensing Properties of Tungsten Oxide, Tin Oxide and Tin-Doped Tungsten Oxide Thin Films for Acetone Gas Detection
摘要： Nowadays, various metal oxide thin films have been used for the purpose of gas sensing. This research depicts a comparison of gas sensing properties among four different metal oxide thin films, namely, tungsten dioxide (WO2), tungsten trioxide (WO3), tin oxide (SnO2) and tin doped tungsten trioxide (Sn-doped WO3), for detecting acetone gas. Each metal oxide thin film was subjected to acetone gas flow of various concentrations and the corresponding changes in resistance were calculated. Characterizations such as x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and gas sensing characterization for recording resistance changes have been performed. Each film was annealed at different temperatures for 1 h (WO2 and WO3 at 500°C, SnO2 at 300°C and Sn-doped WO3 at 400°C) so as to achieve an optimum grain size for sensing. The XRD patterns reveal formation of an orthorhombic phase of WO2, hexagonal phase of WO3 and orthorhombic phase of SnO2. AFM and SEM depict clear images of grain boundaries on the film. SnO2 has been found to be the best thin film for sensing acetone gas. Operational optimum temperature for sensing acetone gas has been calculated for each thin film (260°C for WO2, 220°C for WO3, 360°C for SnO2 and 300°C for Sn-doped WO3). It can detect a very low concentration of 1.5 ppm acetone gas with a good resistance response change of 30%. Various concentrations of acetone gas, namely, 1.5 ppm, 3 ppm, 5 ppm, 7 ppm, 10 ppm, 15 ppm and 20 ppm, have been detected using these metal oxide thin films, and thus the comparison has been made. The response time for SnO2 is approximately 3 min and recovery time is approximately 4 min.
关键词： tungsten oxide,acetone gas detection,topography,tin oxide,Metal oxide thin films,surface metrology,gas sensing,tin-doped tungsten oxide
更新于2025-09-23 15:23:52
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QEPAS Sensor for Simultaneous Measurements of H <sub/>2</sub> O, CH <sub/>4</sub> , and C <sub/>2</sub> H <sub/>2</sub> Using Different QTFs
摘要： A multi-gas quartz enhanced photoacoustic spectroscopy (QEPAS) sensor based on three quartz tuning forks (QTFs) with different response frequencies for trace gas detection was proposed and experimentally demonstrated. Three near-infrared DFB lasers are used to monitor water vapor, methane, and acetylene in the parts per million range. The sensor system was first evaluated for individual H2O, CH4, and C2H2 detection, respectively. Subsequently, the sensor system was evaluated for simultaneous H2O, CH4, and C2H2 detection. Finally, trace gas measurements have been assessed and minimum detection limit (MDL) of 1.3 ppmv at 1368.597 nm for H2O, 79 ppmv at 1653.722 nm for CH4, and 5 ppmv at 1532.83 nm for C2H2 have been demonstrated. The continuous monitoring of H2O, CH4, and C2H2 concentration levels for >3 h indicated the stability of the reported multi-gas QEPAS sensor system.
关键词： Gas detection,QEPAS sensor,multi-component
更新于2025-09-23 15:22:29
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Liquid crystal nose, chiral case: towards increased selectivity and low detection limits
摘要： In this paper, we describe a simple prototype of an olfaction system based on chiral liquid crystals (LCs) and suitable for sensing volatile organic compounds (VOCs). The detection of small concentrations of VOCs is based on measuring weak colour fluctuations on the surface of the LC droplet. Detection of larger concentrations is based on measuring colour changes (or shift of the selective reflection band) and isotropisation transition of the whole droplet. Thus, a broad range of VOC concentrations can be detected by this LC nose.
关键词： gas detection,LC nose,volatile organic compound,olfaction,electronic nose,VOC,liquid crystals,cholesteric
更新于2025-09-23 15:22:29
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High sensitivity fiber optic sensor for hydrogen detection in gas and transformer oil
摘要： This paper reports on the characterisation of a palladium (Pd) based fiber optic hydrogen (H2) sensor for health monitoring of distribution and power transformers in the electrical grid. The sensor consists of a Pd foil, which expands due to H2 absorption, and a fiber Bragg grating (FBG) that measures this expansion. Fifteen sensors were manufactured and characterised in gas and oil environments at various H2 concentrations and temperatures. In gas, the sensors were evaluated at 60°C, 75°C, 90°C, 105°C and 120°C and H2 concentrations from 0.01 to 5%. In oil, the same sensors were evaluated at 90°C and dissolved H2 concentrations from 5 to 2700 ppm. Furthermore, the influence of carbon monoxide (CO), which is often present in transformers and can impact H2 response of the sensor, was investigated. At 90°C in gas, the response to 0.01%, and 5% H2 was on average 28 pm, and 719 pm respectively. At 90°C in oil, the response to 5 ppm, and 2700 ppm dissolved H2 was on average 11 pm, and 763 pm respectively. The average, relative accuracy is better than 20% over the whole measurement range in gas and for measurements above 100 ppm in oil. These specifications make the sensor a promising candidate for online monitoring of H2 in transformers.
关键词： transformer monitoring,Hydrogen,fiber Bragg grating,palladium,gas detection
更新于2025-09-23 15:22:29
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Sensitivity-Selectivity Trade-Offs in Surface Ionization Gas Detection
摘要： Surface ionization (SI) provides a simple, sensitive, and selective method for the detection of high-proton affinity substances, such as organic decay products, medical and illicit drugs as well as a range of other hazardous materials. Tests on different kinds of SI sensors showed that the sensitivity and selectivity of such devices is not only dependent on the stoichiometry and nanomorphology of the emitter materials, but also on the shape of the electrode configurations that are used to read out the SI signals. Whereas, in parallel-plate capacitor devices, different kinds of emitter materials exhibit a high level of amine-selectivity, MEMS (micro-electro-mechanical-systems) and NEMS (nanowire) versions of SI sensors employing the same kinds of emitter materials provide significantly higher sensitivity, however, at the expense of a reduced chemical selectivity. In this paper, it is argued that such sensitivity-selectivity trade-offs arise from unselective physical ionization phenomena that occur in the high-field regions immediately adjacent to the surfaces of sharply curved MEMS (NEMS) emitter and collector electrodes.
关键词： selectivity,gas detection,corona discharge,secondary electron emission,sensitivity,surface ionization
更新于2025-09-23 15:22:29
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Online fire protection technology based on fiber optic gas sensor
摘要： In recent years, the production safety has been paid by a lot of attention. Although the total number of accidents in production safety has shown a downward trend, the serious accidents occur frequently and seriously. The prediction and early warning of spontaneous combustion in coal mines mainly adopts the method of gas index analysis and prediction. The traditional trace gas detection equipment used in spontaneous combustion is mainly chromatographic analysis system, which has some problems such as complicated equipment, complicated operation, slow analysis speed and inability to realize on-line monitoring. The main purpose of this study is to develop a fire risk distribution determination system based on multi-sensor information fusion technology, which is aimed at assisting fire monitoring, fire emergency management, and fire rescue. After using the information from different sensors, the system can give an effective alarm to the fire and can provide the danger degree distribution information of different areas in the building. Based on the development status of fire safety, especially the demand of fire safety for gas detection technology, the tunable laser spectroscopy technology is proposed to solve the demand problem of gas sensing products urgently needed for major fire disasters.
关键词： Optical Fiber,Fire Safety,Optical Fiber Methane Sensor,Multicomponent Gas Detection
更新于2025-09-23 15:21:01
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[IEEE 2018 IEEE International Conference on Consumer Electronics - Asia (ICCE-Asia) - JeJu, Korea (South) (2018.6.24-2018.6.26)] 2018 IEEE International Conference on Consumer Electronics - Asia (ICCE-Asia) - Iterative Normalized Matched Filtering for Detection of Chemical Agents in Hyperspectral Imaging
摘要： Hyperspectral imaging (HSI) can be used to detect a harmful chemical agents’ (CAs’) cloud from a long distance. A normalized matched filter (NMF) is one of the best algorithms to detect CAs in the atmosphere with perfectly known statistics of the background. However, if the background are affected by a CA’s signal, (that is a contamination condition) the performance of the NMF detector is degraded. To design an NMF detector that is robust to contamination, we propose an iterative normalized matched filter (INMF). The proposed algorithm extracts CA-off spectra from the contaminated background spectra dataset using a contaminated NMF detector. And the NMF detector is designed using the extracted CA-off background spectra and this procedure repeats until convergence. Simulation results demonstrate that the proposed algorithm significantly improves the detection performance.
关键词： Gas detection,Normalized Matched Filter,Hyperspectral Image
更新于2025-09-23 15:21:01
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Hydrogen Detection with SAW Polymer/Quantum Dots Sensitive Films
摘要： Regarding the use of hydrogen as a fuel, it is necessary to measure its concentration in air at room temperature. In this paper, sensitive composite films have been developed for surface acoustic wave (SAW) sensors, using quantum dots (QDs) and polymers. Si/SiO2 QDs were used due to having a high specific surface area, which considerably improves the sensitivity of the sensors compared to those that only have a polymer. Si/SiO2 QDs were obtained by laser ablation and analyzed by X-ray diffraction and transmission electron microscopy (TEM). Two types of polymers were used: polydimethylsiloxane (PDMS) and polymethylmethacrylate (PMMA). Polymer and polymer with QDs compositions were deposited on the sensor substrate by drop casting. A heat treatment was performed on the films at 80°C with a thermal dwell of two hours. The sensors obtained were tested at different hydrogen concentrations at room temperature. A limit of detection (LOD) of 452 ppm was obtained by the sensor with PDMS and Si/SiO2 QDs, which was heat treated. The results demonstrated the potential of using QDs to improve the sensitivity of the SAW sensors and to achieve a heat treatment that increases its adsorption capacity of the gas molecules.
关键词： quantum dots,gas detection,gas sensor,hydrogen sensor,surface acoustic wave,polymer,composite,SAW sensor
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - All-Fiber Source for Generation of Tunable Broadband f <sub/>CEO</sub> -Free Mid-IR Pulses for Laser Spectroscopy Applications
摘要： Recent decade brought a tremendous progress laser-based gas detection techniques. This progress would not be possible without the relentless devotion of the scientific community in developing state-of-the-art sources capable of targeting strong absorption lines of gases localized in the mid-infrared (mid-IR) wavelength region. Although narrowband, semiconductor-based mid-IR lasers offer non-complex implementation their tuning range is usually limited to several cm-1. Therefore designing a sensor capable of simultaneous monitoring of several gas species, even with absorption profiles clustered nearby, requires incorporating individual expensive quantum cascade laser (QCL) or interband cascade laser (ICL) sources into a single platform. Recent development of reliable mid-IR comb sources, combined with clever methods of signal processing allowed for designing gas sensors capable of simultaneous monitoring of several gas analytes in fractions of a second [1]. Obtaining broadband pulsed radiation in the mid-IR region is usually accomplished by utilizing nonlinear conversion or in recently presented on-chip QCL combs [2]. Although QCL combs offer compactness and efficiency they do not allow straightforward control of the repetition frequency (frep) or the carrier-envelope offset frequency (fCEO), which are critical in some particular cavity-enhanced comb-based sensing techniques, e.g. Vernier spectroscopy [3]. Here we present a fully-fiberized, fCEO-free mid-IR optical frequency comb source capable of covering 6 – 9 μm wavelength region with tunable frep. The setup of the source is presented in Fig 1. The heart of the source is a ring-cavity graphene mode-locked laser generating sub-250 fs pulses at 1560 nm and frep of 100 MHz. The pulses are split using a 50/50 coupler and directed to separate sections of the source. In the blue section the source the pulses are amplified to 80 mW in an all-fiber-based chirped pulse amplifier (CPA) and recompressed in a 8 m-long section of PM1550 fiber to ~200 fs. In the red section a custom manufactured nonlinear fiber with tailored dispersion (PCF) is utilized to soliton-shift the 1.56 μm pulses into the 1.9 - 2 μm wavelength region. Subsequently the pulses are amplified in a CPA and recompressed to ~200 fs. Combined 1.56 and 2 μm pulses are focused on a 3 mm-long orientation patterned gallium phosphide (OP-GaP) crystal to generate mid-IR radiation via differential frequency generation (DFG). Since both pulses originated from the same ML source, the generated mid-IR frequency comb is inherently fceo-free and can be used in laser-based gas sensors requiring stable carrier-envelope offset. The source is built entirely from PM single-mode fibers.
关键词： mid-IR,optical frequency comb,laser spectroscopy,fCEO-free,gas detection
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Photothermal Gas Detection of CO <sub/>2</sub> in an Intracavity Solid-State Laser Configuration
摘要： Laser spectroscopy has proven to be a powerful tool for quantitative and selective measurements of gas samples. Numerous techniques have been developed throughout the recent decades. This progress has been driven mostly by the growing demand on sensitive sensors, also for out-of-lab applications. Here we describe a new gas detection technique, which relies on photo-thermal (PT) effects. In PT spectroscopy the gas sample concentration can be derived by measuring a change in the refractive index (RI) of the excited gas particles. This is usually achieved by exciting the gas particles using a radiation source and by measuring the small variations of the RI (usually in the range of 10-5), e.g. in an interferometric sensor configuration, which is complicated and prone to mechanical and acoustic noise. Moreover, appropriate construction of a PT sensor enables encoding the gas concentration into frequency variations (similarly to dispersion spectroscopy), which provides a baseline-free measurement. Here we propose a novel, patent-pending configuration, which is non-complex, cost effective, miniaturized and offers detection limits at least comparable with other methods, having similar complexity, e.g. quartz enhanced photo-acoustic spectroscopy. Base of the sensor is a standard configuration of a monolithic, solid-state laser based on Nd:YVO4 active crystal and a YVO4 birefringent crystal ensuring single polarization operation of the laser at 1064 nm. To enable implementing PT gas detection an intentional air-gap has been obtained inside the resonator by separating the output mirror with a 2x2x2mm3 quartz crystal. In this particular experiment the air gap was filled with CO2 under ambient pressure and excited with an auxiliary fiber laser targeting a strong absorption line localized at 2003,5 nm. Due to the PT effect the density of the excited gas changes, which results in a change of its RI. A change of RI inside the solid-state laser resonator results in a slight variation of the optical pathlength and hence is directly translated to frequency changes of emission of the solid-state laser. The optical frequency changes are detected in a heterodyne configuration (the reference laser emission was obtained in the same crystal structure to minimise noise; the gas is excited in the path of only one of the emissions). The 2 μm excitation laser was modulated with a f0=1 kHz sinewave function and tuned across the absorption line. The induced PT effect was conveniently filtered-out at 2xf0 using a lock-in amplifier. The schematic of the sensor configuration, along with 2f signal registered for a 1000 ppmv and 200 ppmv CO2 sample is depicted in figure 1.
关键词： photothermal gas detection,refractive index,intracavity solid-state laser,CO2,heterodyne configuration
更新于2025-09-16 10:30:52